If you keep reinforcing that you love them unconditionally, they’ll feel safe coming to you when they’re ready to seek help.
However, depending on your relationship to the person, you want to be mindful that you set boundaries around behaviors rather than enabling them. For example, if your partner has been struggling with an eating disorder and has replaced your evening meal together with the gym, it’s okay to say, “I miss you. I miss having dinner together after work. I know the eating disorder might be telling you the gym is more important than me, but I want you to know that’s just the eating disorder trying to come between us. It leaves me feeling neglected.”
Because eating disorders can be so manipulative and all-consuming, it can sometimes be helpful to remind your loved one how it’s affecting you — just be sure to do it in a very compassionate way that puts the blame on the disorder rather than the person.
Telling someone they’re “not fat” can just reinforce their belief that they need to be thin to be loved.